Modern internal combustion engines use heat recuperation from the exhaust gas which is produced during the combustion operation in order to increase efficiency. What are known as exhaust gas evaporators are based on this operative principle, which exhaust gas evaporators, as part of an exhaust gas system which interacts with the internal combustion engine, are flowed through both by exhaust gas and a liquid operating medium. Here, the hot exhaust gas evaporates the liquid operating medium which is present in gas form after the evaporation and can be expanded during the course of a Rankine process, as a result of which mechanical work is produced. Said mechanical work can be coupled into the drive train of the internal combustion engine in order to increase efficiency.
Conventional exhaust gas evaporators are typically equipped with a housing of sufficient dimensions, and are mounted on the vehicle frame together with further components which act in the exhaust gas section of the internal combustion engine. A further component of this type is often an exhaust gas aftertreatment device which is connected upstream of the exhaust gas evaporator. It serves to treat and purify the pollutants which are present in the exhaust gas before they are introduced into the exhaust gas evaporator and are subsequently released by the latter into the surroundings of the motor vehicle. Said exhaust gas aftertreatment device is also usually equipped with a separate housing and is fastened to the vehicle body by means of suitable fastening means in an analogous manner to the exhaust gas evaporator. The necessary fluidic connection between the exhaust gas aftertreatment device takes place as a rule via a suitably configured exhaust gas pipe which is arranged between the exhaust gas aftertreatment device and the exhaust gas evaporator.
It proves a problem in exhaust gas systems of this type that the components which are typically configured separately and are equipped in each case with an individual housing are associated with a considerable requirement for installation space. Said installation space is usually available only to a limited extent in modern motor vehicles, however. In addition, what is known as an exhaust gas bypass line is as a rule necessary, in order to make bypassing of the exhaust gas which exits from the exhaust gas aftertreatment device past the exhaust gas evaporator directly into the surroundings possible when required, and therefore to avoid an input of heat into the Rankine circuit. This can become necessary, for example, for safety reasons in the case of an emergency switch-off of the system. The arrangement of a bypass line of this type also requires additional installation space, in particular in conjunction with a valve device for closing the bypass line.
Against said background, EP 2 110 527 B1 discloses a commercial vehicle having an internal combustion engine and a heat recovery system which interacts with the latter. A medium circuit of said heat recovery system is arranged in a silencer which in turn is arranged in an exhaust gas section of the internal combustion engine of the motor vehicle.